The present invention concerns a smart card and more precisely a smart card comprising a card bearing a module consisting of a support itself supporting at least one electronic chip, said support being fixed on a surface of the card.
A known smart card consists of a card made of plastic material of standardised format, two formats of which are the “bank card” type defined by ISO 7810 and the SIM “mini-card” type for mobile telephony. It bears an electronic module consisting of a support formed from a sheet of dielectric material possibly provided with printed circuits and supporting an electronic chip, for example an electronic memory. As a general rule, this chip is glued on one face of the support and protected by a coat of epoxy resin forming an extra thickness on the support. Hereinafter this face will be referred to as the rear face.
For fixing the module on the card, the latter comprises a first cavity of a first depth and a second cavity of a second depth implemented in the bottom of the first cavity and intended to receive chip and resin. The support is glued in the first cavity around the second cavity. The first cavity has a total surface equal to the surface of the module which is therefore installed by flush fitting therein. The thickness of such a card is standardised and approximately 800 microns, the first depth is approximately 200 microns and the second depth is approximately 400 microns.
What is sought at present is to store a large amount of data on such smart cards and consequently to install larger modules or to install several modules on a single card. This is in order to produce high-capacity memory cards capable of storing directories, music, films, etc.
The arrangement used at present has several problems.
The gluing surface for the module support can prove to be insufficient and lead to poor fixing of said module, in particular in the case of a large-sized chip. This is because this gluing surface is limited to the bottom of the first cavity apart from the second cavity receiving the chip and its protective resin. Consequently, the greater the total surface of the chip or chips, the more insufficient this gluing surface proves to be since the ratio of module surface to gluing surface decreases.
This arrangement also poses manufacturing problems. In view of the depth of the first cavity, approximately 200 microns, this cavity must be implemented at a distance from the edges of the card imposed by the requirements of the moulding process. This distance must also be approximately 200 microns minimum. In fact it is difficult and even impossible to reduce this distance, since it is impossible to inject the plastic material onto a very thin wall. This is a manufacturing requirement running counter to the need to increase the format of the modules, the format of the card being standardised.